This invention generally relates to a self-cleaning ink jet printer and methods for cleaning the same, and more particularly to a print head cleaning assembly including a roller for use in cleaning the print head surface and ink nozzles for an ink jet printer having a fixed canopy-type gutter.
An ink jet printer produces images by ejecting ink droplets onto a receiver medium in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the capability of the printer to print on plain paper mediums are largely responsible for the wide acceptance of ink jet printers in the marketplace.
xe2x80x9cOn demandxe2x80x9d ink jet printers utilize a pressurization actuator to produce the ink jet droplet at orifices of a print head. In this regard, either one of two types of actuators may be used including heat actuators and piezoelectric actuators. With heat actuators, a heater placed at a convenient location heats the ink and a quantity of the ink will phase change into a gaseous steam bubble and raise the internal ink pressure sufficiently for an ink droplet to be expelled onto the recording medium. With piezoelectric actuators, a piezoelectric material possessing properties such that an electric field is produced when a mechanical stress is applied. The converse also holds true; that is, an applied electric field will produce a mechanical stress in the material. Some naturally occurring materials possessing these characteristics are quartz and tourmaline. The most commonly produced piezoelectric ceramics are lead zirconate titanate, barium titanate, lead titanate, and lead metaniobate.
In the case of xe2x80x9ccontinuousxe2x80x9d ink jet printers, electrostatic charging tunnels are placed close to the point where ink droplets are being ejected in the form of a stream. Selected droplets are electrically charged by the charging tunnels. The charged droplets are deflected downstream by the presence of deflector plates that have a predetermined electric potential difference between them. A gutter may be used to intercept the charged droplets, while the uncharged droplets are free to strike the recording medium.
Recently a new type of continuous ink jet printer has been disclosed. U.S. Pat. No. 6,079,821 which issued to Chwalek et al. on Jun. 27, 2000, describes a continuous ink jet printer in which on demand asymmetric heating of an ink jet causes selected drops to deflect. In one mode of operation, selected drops are deflected toward an image-recording medium while the other drops are intercepted in a canopy-type gutter that is placed in close proximity (for example, 3 mm) to an ink jet nozzle plate.
Inks for high-speed inkjet printers, whether of the xe2x80x9ccontinuousxe2x80x9d or xe2x80x9cpiezoelectricxe2x80x9d type, must have a number of special characteristics. For example, the ink should incorporate a nondrying characteristic, so that drying of ink in the ink ejection chamber is hindered or slowed to such a state that by occasional spitting of ink droplets, the cavities and corresponding nozzles are kept open. The addition of glycol facilitates free flow of ink through the ink jet chamber. Of course, the ink jet print head is exposed to the environment where the ink jet printing occurs. Thus, the previously mentioned nozzles are exposed to many kinds of air born particulates. Particulate debris may accumulate on surfaces formed around the nozzles and may accumulate in the nozzles and chambers themselves. That is, the ink may combine with such particulate debris to form an interference that blocks the nozzle or that altars surface wetting to inhibit proper formation of the ink droplet. The particulate debris should be cleaned from the surface and nozzle to restore proper droplet formation. In the prior art, this cleaning is commonly accomplished by brushing, wiping, spraying, vacuum suction, and/or spitting of ink through the nozzle.
Thus, ink jet printers can be said to have the following problems: the inks tend to dry-out in and around the nozzles resulting in clogging of the nozzles; and the wiping of the nozzle plate causes wear on plate and wiper, the wiper itself producing particles that clog the nozzle. In addition, cleaning an ink jet nozzle plate that has limited accessibility due to the placement of a fixed gutter poses extra demands on the design of cleaning members and on methods used.
Ink jet print head cleaners are known. For example, a print head wiping system for inkjet print heads is disclosed in U.S. Pat. No. 5,614,930, entitled xe2x80x9cOrthogonal Rotary Wiping System For Inkjet Printheadsxe2x80x9d issued Mar. 25, 1997 in the name of William S. Osborne et al. The Osborne et al. patent discloses a rotary service station, which incorporates a wiper-supporting tumbler. The tumbler rotates to wipe the print head along a length of a linearly aligned nozzle. In addition, a wiper scraping system scrapes the wipers to clean the wipers. However, Osborne et al. do not disclose use of an external solvent to assist cleaning and also does not disclose complete removal of the external solvent. In addition, a wiper scraping system is limited by the size constraints imposed by the print head itself. This is particularly true for fixed gutter inkjet print head systems, which partially encloses the print head surfaces. Fixed gutter systems require a mechanism that can work within small tolerances imposed by the integrated gutter in order to clean the print head. The Osborne et al. cannot tolerate the stresses demanded by the tight spacing and limited size of current ink jet print heads.
Therefore, there is a need to provide a suitable ink jet printer with a cleaning mechanism, and method of assembling the same, wherein the cleaning mechanism is capable of cleaning the print head surface within the confines of small tolerances and limited spacing. There is also a need to supply cleaning liquid to lubricate and aid cleaning in a manner that does not cause wear of the print head nozzle plate. Furthermore, there is a need for a cleaning mechanism that can operate within the limited spacing imposed by a fixed canopy-type gutter.
It is an object of the present invention to provide a self-cleaning ink jet printer with a cleaning mechanism and method of assembling the same, wherein a surface of a print head belonging to the printer is effectively cleaned.
It is another object of the present invention to provide an ink jet print head assembly that includes a cleaning mechanism and method of assembling the same that can be utilized in fixed gutter continuous ink jet printers.
With the above objects in view, disclosed is a cleaning mechanism composed of a print head cleaning assembly for use in a self-cleaning printer. The self-cleaning printer includes a print head having a print head surface and an ink channel therein, and a structural member that functions as a gutter for collecting ink disposed opposite to the print head surface. The cleaning mechanism is adapted to clean contaminant from the print head surface.
According to an exemplary embodiment of the present invention, a self-cleaning printer is disclosed, wherein the self-cleaning printer includes a print head defining a plurality of ink channels therein, each ink channel terminating in a nozzle. The print head also has a surface thereon surrounding all the nozzles. The print head is capable of letting ink through the nozzles, such that ink jets are subsequently heated to cause ink drops to form and to selectively deviate for printing. Ink drops are intercepted by either a receiver medium, such as paper, or a gutter. In one method of operation, ink is selectively deflected onto a receiver supported by a platen disposed adjacent the print head, while the non-deflected ink drops are intercepted by the gutter.
Ink intercepted by the gutter may be recycled. Contaminant such as an oily film-like deposit or particulate matter may reside on the surface and may completely or partially obstruct the nozzle. The oily film may be, for example, grease and the particulate matter may be particles of dirt, dust, metal and/or encrustations of dried ink. Presence of the contaminant interferes with proper ejection of the ink droplets from their respective nozzles and therefore may give rise to undesirable image artifacts, such as banding. It is therefore desirable to clean the contaminant from the surface and the nozzles.
Therefore, a cleaning mechanism is disposed relative to the surface and/or the nozzles so as to direct a print head cleaning assembly to clean the contaminant from the surface and/or nozzle via contact with a roller. As described in detail herein, the cleaning mechanism is configured to introduce cleaning liquid to the print head cleaning assembly to facilitate and augment cleaning by the roller. In one embodiment, the roller comprises a rotating shaft surrounded by a covering made of a sponge-like porous material. A driver connected and/or integrated with the rotating shaft provides the movement of the roller. The driver is driven by a motor.
In a preferred embodiment, cleaning liquid is supplied to the print head surface through channels provided in the gutter. The sponge-like material assists the contaminants in adhering to the roller during the back and forth movement of the roller across the print head surface.
A feature of the present invention is the provision of a mechanism to align and transport the roller during cleaning operation.
Another feature of the present invention is the provision of an ultrasonic transducer to energize the cleaning action by the roller and the cleaning liquid.
A technical advantage of the present invention is that the cleaning mechanism belonging to the invention cleans the contaminant from the surface and/or nozzle(s) in the confined space between the print head surface and the fixed gutter.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description taken in conjunction with the appended drawings, which show and describe illustrative embodiments of the invention.